The present invention relates to drive controllers as used in machinery drives, for motor control and the like. In particular the present invention relates to a drive controller operator interface and serial protocol therefor.
In an industrial plant, to enable machinery to operate, for example, a conveyor belt in a production line, pumps, compressors, ventilation systems, hoisting gear, cranes etc electric motors are employed. Electric motors may drive machinery directly by means of a clutch, by way of a transmission belt, hydraulic path, or some other means. The motor itself may drive a low wattage (less than 100 W) application such as a drive for a laboratory centrifuge or a high wattage (greater than 300 KW) application such as a steel press. The motors can be DC or AC, single phase or multiple phase.
Electric motors and other electrical devices are typically controlled by inverters which convert input power to control input signals for the motor or other electrical device. Inverters are controlled by a control panel. The inverters themselves are typically placed in a rectangular box dimensioned 10 cmxc3x9715 cmxc3x9720 cm but, depending on power requirements, may be much smaller or much larger. Conveniently the converters are packaged with other electrical control equipment.
Since the inverter controllers include keyboard controls and LED/LCD displays, it has been found that the controllers represent a significant cost of the inverters. To overcome this or for other reasons such as overall control integration, inverters have been remotely controlled by software using cabling operated on RS232 protocols or similar. However, it has been found in some applications, that cabling is susceptible to interference.
An alternative system is to have single removable keypad/display unit controller which can serve a number of drives. The single key pad/display unit controller is selectively attached to a number of drives, the instructions downloaded to the drive and then keypad/display unit controller is removed. Alternatively a number of removable keypad/display unit controllers may be employed by a limited number of users. One advantage of this type of system is that the drives may not be controlled by those not authorised. These keypad/display unit controllers shall be referred to hereinafter as a BOP (Basic Operator Panel). BOP""S have been found to be sufficiently flexible to accommodate various styles of LCD, such as simple four digit displays and are provided with varying numbers of pinouts, depending on the application. In use, a BOP is attached to a drive and co-operating connector pins and sockets (pinouts) enable single signals to be transmitted. A BOP operator will instruct a memory associated with the drive via the keypad using a serial data link. Alternatively an optical link will transfer data in which case the BOP has an integrated electrical cell to provide electrical power; be coupled with a power source associated with the drive or otherwise be connected to a power source.
One problem associated with this system is that standard signaling protocols do not provide sufficient data carrying capacity to enable data to be transferred as effectively as possible. Another problem that has arisen is that a BOP cannot necessarily be used with other types of devices.
The present invention seeks to provide an improved drive controller.
In accordance with a first aspect of the present invention there is provided a drive controller and operator panel operable to control a drive, wherein the operator panel is removable with respect to the drive controller and includes data input means and a data transfer port; wherein the drive controller is operatively connected to the drive and includes a data transfer port which is operable to co-operate with the data transfer port of the operator panel whereby to enable the drive controller and the operator panel to communicate data by means of a serial protocol; wherein the serial protocol includes data indicating the device type of the device transmitting the data.
The data transfer can be effected by means of optical signals, electrical signals, or wireless signals. Accordingly, co-operating optical transmitter and receiver pairs, co-operating plug and sockets and co-operating wireless transceiver means are required. The display on the operator panel can be an LCD or LED display. Preferably the LCD or LED display is triplexed whereby the amount of signaling can be reduced. Where there are micro-input/output pins, this means that the number of pins can be reduced.
Conveniently the protocol includes a cyclic redundancy check byte. Conveniently the protocol also includes a data field which is a field of variable length. In accordance with a further aspect of the present invention there is provided an operator panel operable in the above arrangement. In accordance with a further aspect of the invention there is provided a drive controller operable in the above arrangement.
In accordance with a still further aspect of the present invention there is provided a signaling protocol for data communication between a drive controller and an operator panel, whereby to control a drive, wherein the protocol includes data indicating the device type in respect of the device transmitting the data.
Preferably the protocol includes a data field which is a field of variable length. Preferably the signalling protocol includes a cyclic redundancy check bit.